EP0306630B1 - Process for the regeneration of the soot filter in a diesel exhaust engine system - Google Patents

Description

The invention relates to a method for regenerating a soot filter system in the exhaust tract of a diesel engine with a supercharger according to the preamble of claim 1.

From JP-A-60-216017, an exhaust gas treatment system in an internal combustion engine provided with a charging device is known. To initiate regeneration when the internal combustion engine is working at low speed and low load, the speed of the turbine of the charging device is increased via a flap control in order to increase the boost pressure. As a result, a larger amount of charge air is fed to the burner to stabilize the combustion thereof. The burner is fed with a prepared mixture of fuel and combustion air, and the critical operating range of the burner at low speed and low load on the internal combustion engine is stabilized by increasing the boost pressure of the charging device. As a result, changes in the charging device of an internal combustion engine are essential.

From JP-A-61-93219 is an internal combustion engine with a soot filter system and a supercharger known, in which charge air is fed into the exhaust line going to the soot filter with the aid of control valves, to support the regeneration of the soot filter system. Here, too, there are visual difficulties when initiating and carrying out the regeneration in all operating areas and load areas of the internal combustion engine.

There are also burners for a regeneration device which can be operated with compressed air, but relatively high pressures of the combustion air required for combustion are required. Therefore, additional compressors are required which lead to an additional increase in the cost of such a soot filter system and which consume a relatively large output here.

In the older DE-A-37 17 140, a soot filter system is specified in the exhaust tract of a diesel engine, in which the burner of the regeneration device is operated with exhaust gas from the diesel engine. Here, it has been shown that under n-knowing operating conditions in the engine map of the diesel engine, the oxygen content of the exhaust gas can be insufficient for the burner to work reliably. Furthermore, there is also the difficulty that the gas generated by the burner and used to regenerate the soot filter contains only a little oxygen which is required for the soot combustion during regeneration.

In recent years, diesel engines have become increasingly popular Call charging or turbocharging applied, in which air under a boost pressure is fed to the cylinders of the internal combustion engine. Such a supercharger usually comprises a turbine in the exhaust tract of the diesel engine and an associated compressor, the output of which is connected to the air inlet line or the air inlet lines of the diesel engine. With such a so-called supercharged diesel internal combustion engine, higher outputs and an improved combustion efficiency are obtained.

The invention is based on the call to provide a method for regenerating a soot filter system in the exhaust tract of a diesel internal combustion engine with a charging device, in which one obtains stable operation of the burner of the regeneration device in the area of the entire engine map of the internal combustion engine.

According to the invention, a method for regenerating a soot filter system in the exhaust tract of a diesel internal combustion engine with a charging device is specified for this purpose, which has the features of claim 1.

In this soot filter system according to the invention, the air which is at a predetermined boost pressure, which is generated by means of the charging device, is fed to the burner, so that it can be used as combustion air for the burner in admixture with exhaust gas. In such a turbocharged diesel internal combustion engine, the air under the desired pressure is therefore the So-called charge air, which is also used according to the invention for operating the burner of the regeneration device of the soot filter system. Thus, in the soot filter system according to the invention, additional compressors for the generation of pressurized air, which serves as combustion air for the burner, can be dispensed with, so that the entire soot filter system is considerably simplified. On the other hand, the burner can also be operated reliably in the entire engine map of the diesel engine, since it is at least not exclusively dependent on the oxygen content of the exhaust gas. This also simplifies the control of such a burner for the soot filter regeneration and one obtains an improved operational reliability without having to put up with a relatively large and cost-intensive additional design effort.

Since the burner is also supplied with exhaust gas, see in particular possible difficulties that are caused by the fact that, for example, when the diesel engine is idling, the pressure of the charge air supplied by the charging device is insufficient to ensure reliable operation of the burner in this idle operating range to guarantee. Since the burner is also supplied with exhaust gas, the burner can be operated with exhaust gas when the diesel engine is idling, which has a relatively high oxygen content in the idling operating state, which is sufficient for the burner to work reliably. Furthermore, one obtains such for the burner in the entire engine map Working conditions that always make the burner reliably flammable. When the engine load is low, i.e. when the charge pressure of the charge air generated by the charging device is low, little charge air is fed to the burner, but the simultaneously mixed exhaust gas from the exhaust tract has a relatively high oxygen content, so that when the burner is operated in this load state, there is none Problems. With a large engine load, however, the charge air supplied by the charging device is under a high boost pressure, so that a lot of charge air can be fed into the burner and the burner can work reliably in this operating state, although the exhaust gas in the exhaust tract has a relatively low oxygen content in this area of the engine map Has. By supplying the charge air to the burner, the low oxygen content of the exhaust gas can thus be automatically compensated for, so that there are no problems with operating the regeneration device in this engine load range either. By this measure that the burner of the regeneration device is fed with both exhaust gas and charge air from the charging device, one thus obtains an automatic, favorable operating range for the burner of the regeneration device, which is regulated by the charging pressure of the charging air supplied by the charging device.

Depending on the design of the soot filter system, which, in advantageous further refinements according to the invention, can comprise two or more soot filters connected in parallel, such a can expediently be used according to the invention Interpretation are made that a common burner is provided for the regeneration, so that in the entire soot filter system, even if it comprises several soot filters, only a single burner is required to operate un as little as possible.

Alternatively and in particular when using so-called multi-filter systems, it may also be expedient to assign a burner to each soot filter so that the number of burners corresponds to the number of soot filters.

In the burner of the regeneration device, which is supplied with both exhaust gas and charge air from the charging device, it has proven expedient to arrange the burner or burners directly in the exhaust gas line or the exhaust gas lines, so that the burner is continuously flowed through by the exhaust gas.

Alternatively, however, the burner or burners can also be arranged in parallel with the exhaust pipe (s) in order to avoid a constant flow through the burner (s) with exhaust gas.

In order to be able to change the charge air supply to the burner or burners, it is advantageous if a regulating device is present in the connecting line between the burner or burners in the charging device. This can expediently be formed by a valve and preferably by a solenoid valve.

To allow passage of the exhaust gas at a To prevent mixed feeding of the burner with exhaust gas and charge air, it may be expedient to arrange a check valve in the connecting or connecting lines between the charging device and the burner, which prevents exhaust gas from entering the connecting line or connecting lines.

Fig. 1

eine schematische Ansicht einer Rußfilteranlage mit einem einzigen Rußfilter, bei der der Brenner der Regenerierungseinrichtung sowohl mit Abgas im Abgastrakt der Diesel-Brennkraftmaschine als auch mit Ladeluft von der Aufladeeinrichtung versorgt wird,

Fig. 2

eine Fig. 1 ähnliche Ausführungsvariante, bei der der Brenner der Regenerierungseinrichtung jedoch nicht im Abgastrakt der Diesel-Brennkraftmaschine liegt, sondern hierzu parallel geschaltet ist,

Fig. 3

eine schematische Ansicht einer Rußfilteranlage mit zwei parallel geschalteten Rußfiltern als Beispiel eines Mehrfilter-Systems, und

Fig. 4

eine schematische Ansicht einer Ausführungsvariante eines Mehrfilter-Systems, bei dem ähnlich wie in Fig. 3 beispielhaft zwei parallel geschaltete Rußfilter vorgesehen sind.

The invention is explained below using examples with reference to the accompanying drawings. It shows:

Fig. 1

2 shows a schematic view of a soot filter system with a single soot filter, in which the burner of the regeneration device is supplied both with exhaust gas in the exhaust tract of the diesel engine and with charge air from the charging device,

Fig. 2

1 similar embodiment variant, in which the burner of the regeneration device is not located in the exhaust tract of the diesel internal combustion engine, but is connected in parallel to this,

Fig. 3

a schematic view of a soot filter system with two soot filters connected in parallel as an example of a multi-filter system, and

Fig. 4

is a schematic view of an embodiment of a multi-filter system, in which two soot filters connected in parallel are provided as in Fig. 3 as an example.

In the figures of the drawing, identical or similar parts are provided with the same reference symbols. To distinguish them, the design variants of the soot filter system shown in the figures of the drawing are denoted overall by 1a, 1b, 1c and 1d. The soot filter systems 1a to 1d are intended for supercharged diesel engines.

The soot filter system 1 a shown in FIG. 1 is intended as an example of a four-cylinder diesel internal combustion engine which has a charging device 2. The supercharger 2 comprises a turbine 3, which is arranged in an exhaust tract 4 of the diesel engine 5, and a compressor 6, which also sucks in air through a suction filter 7, compresses it and introduces it through an outlet into the inlet system 8 of the diesel engine 5.

The regeneration device of the soot filter system 1a is denoted overall by 9. The regeneration device 9 has a burner 10, which is arranged in the exhaust tract 4 of the diesel engine 5. In the exhaust tract 4, the burner 10 is followed by a soot filter 11 in the example shown.

In the example shown, a connection line 12 connects the inlet system 8 of the diesel internal combustion engine 5, which is connected to the outlet of the compressor 6 of the charging device 2, and connects the inlet system 8 to the burner 10. As shown, a solenoid valve 13, for example, can be arranged in the connecting line 12 as a control device.

In this example, the soot filter system 1a is shown the burner 10 of the regeneration device 9, when the soot filter 11 is to be regenerated, ie the soot particles collected there are to be burned off, is supplied with exhaust gas in the exhaust tract 4 as well as with charge air from the charging device 2 via the connecting line 12. With the help of the solenoid valve 13 in the connecting line 12, the amount of charge air supplied to the burner 10 can be regulated.

If the diesel engine 5 is idling and the burner 10 of the regeneration device 9 is to be put into operation, the burner 10 essentially serves the exhaust gas in the exhaust tract 4 as a combustion medium, since the charging device 2 cannot generate charge air with sufficient pressure in idle mode . However, since the exhaust gas in the idle mode of the diesel engine 5 has a high oxygen content, the burner 10 can also be ignited and operated in the idle mode. As soon as the engine load rises, but is still in the low load range, for example, the charging device 2 supplies charge air with a low charge pressure, which is then additionally fed into the burner 10. In this operating range of the diesel internal combustion engine 5, the oxygen content in the exhaust gas then drops, so that reliable ignition and operation of the burner 10 is ensured thanks to the supply of the charge air. When the engine is under heavy load, the charge pressure of the charge air from the charging device 2 is likewise correspondingly high, while the oxygen content in the exhaust gas becomes low, so that sufficient charge air is branched off from the charging device 2 so that the burner is reliable even in this operating state of the diesel engine 5 can work. In the inventive design of the method for regenerating the soot filter system 1 a, it is thus possible that, depending on the operating state of the diesel internal combustion engine 5, the charging air 2 of the charging device 2 is always automatically fed in via the connecting line 12 in the burner 10 such operating conditions are present that this can be ignited and operated reliably.

The embodiment variant of a soot filter system 1b shown in FIG. 2 is also a so-called single-filter system, the illustration of the diesel internal combustion engine 5 and the further details of the charging device 2 being omitted. As a significant difference to the soot filter system 1a, the burner 10 'in the soot filter system 1b in FIG. 2 is not arranged in the exhaust tract 4, but is connected in parallel to it, i.e. it lies in a so-called bypass branch. In the example shown in FIG. 2, the burner 10 'is supplied with both exhaust gas from the exhaust tract 4 and charge air from the charging device (not shown). All other details shown in Fig. 1 correspond mutatis mutandis in the embodiment of the soot filter system 1b. Although it is not shown in more detail, it may be expedient to arrange a check valve in the connecting line 12, which prevents exhaust gas from passing through the exhaust tract 4 in the direction of the charging device 2 or the inlet system 8 of the diesel internal combustion engine.

In Fig. 3, the soot filter system is generally designated 1c and, as an example of a multi-filter system, a design with two soot filters 11, 11 'connected in parallel is selected here. Here, the exhaust tract 4 is branched and the soot filter 11 or 11 'is then arranged in the respective branch formed. At the branching point of the exhaust tract 4, a flap 14 is arranged, which serves as a control device and which directs the exhaust gas flow according to its position through a soot filter 11 as shown in the example shown. If this soot filter 11 has to be regenerated, the flap is rotated by approximately 90 ° from the position shown in FIG. 3 and the exhaust gas in the exhaust tract 4 is then fed to the soot filter 11 '. The total designated 9 regeneration device in this example comprises a single burner 10˝, which is intended together for the regeneration of both soot filters 11, 11 '. The output of the burner 10˝ opens into the branching area of the exhaust tract 4 and by means of the flap 14, the hot exhaust gas flow generated by the burner 10 "is then directed to the soot filter 11 or 11 'to be regenerated The charging device shown is supplied via the connecting line 12. Furthermore, a connecting line 15 is shown, via which a connection is established between the exhaust gas tract 4 and the connecting line 12 coming from the charging device 12. Via this connecting line 15, exhaust gas is mixed into the charge air flow in the connecting line 12, so that the burner 10˝ is supplied with a mixture of charge air and exhaust gas from the exhaust tract 4.

Another embodiment variant of the soot filter system is denoted overall by 1d in FIG. 4. In contrast to Fig. 3 branch in the embodiment of FIG. 4 from a front silencer 16 in the exhaust tract 4 two parallel exhaust pipes 17, 18, in each of which a burner 10 '' is arranged. The burners 10'˝ are each flaps 19, 19 'upstream, and the burners 10˝' is a soot filter filter 11, 11 'downstream. The flaps 19, 19 'serve, for example, to decouple the filter 11 from the flow through the exhaust gas in the closed state in order to regenerate this filter 11, while the exhaust gas is then cleaned by the second soot filter 11' connected in parallel. The flap 19 'in the exhaust pipe 18 is then open. 17 arranged burner 10'˝, which is supplied with charge air from the charging device, not shown, is then ignited and put into operation so that it supplies 11 hot combustion gases for the regeneration of the soot filter. If in this example the flap 19 or 19 'is leaking in the closed state, then a further admixture of exhaust gas from the exhaust tract 4 takes place via the flap gap formed here. The flaps 19, 19' are designed such that in the closed position there is always a certain leakage path is present and the burners 10˝ 'in Fig. 4 are operated in the mixed operation of charge air and exhaust gas in the exhaust tract 4.

When operating the burners shown in the drawings, i.e. if these are supplied with exhaust gas and charge air, the mode of operation explained at the outset in connection with FIG. 1 is obtained.

Of course, in the embodiments according to FIGS. 2 to 4 control valves and the like. be provided in the connecting line 12 and / or the connecting line 15 in Fig. 3 to the charge air supply to the burner 10, 10 '. 10˝, 10'˝ to control in a corresponding manner. Of course, the invention is not limited to the double filter system or single filter system of a soot filter system 1a to 1d shown as an example, but more than two soot filters can of course also be provided, the design then being analogous to FIGS. 3 to 4 is hit. The number of soot filters 11 to 11 'provided in the soot filter system 1a to 1d essentially depends on the size of the diesel internal combustion engine and / or possibly the available space. In double and multi-filter systems, there is the advantage that relatively little air is taken from the charging device for operating the burners 10, 10 ', 10˝, 10'˝ of the charging device, in order to have an adverse effect on the charging operation of the diesel engine 5 to prevent. This advantage is particularly important if, in the soot filter system 1a to 1d, exhaust gas is added from the exhaust tract 4.

Claims (8)

1. Process for regenerating a soot filtering unit in the exhaust section of a diesel internal combustion engine with a supercharger, whose compressor is connected via an outlet with an intake system of the internal combustion engine, at least one soot filter located in an exhaust pipe and a regenerating device with at least one burner, to which is supplied an air charge under the supercharging pressure of the supercharger, characterized in that for stabilizing the operation of the burner in the case of a varying load state of the internal combustion engine the burner of the regenerating device is supplied both with exhaust gas from the internal combustion engine and with the air charge from the supercharger in such way that when the internal combustion engine is idling or under low load the exhaust gas is fed in as combustion gas, whereas under high load the air charge is increasingly additionally fed in.

2. Process according to claim 1, characterized in that in the case of two or more parallel-connected soot filters for regeneration, use is made of a joint burner.

3. Process according to claim 1, characterized in that with two or more parallel-connected soot filters a burner is used for each of them.

4. Process according to one of the preceding claims, characterized in that the burner or burners are positioned in the exhaust pipe or pipes.

5. Process according to one of the claims 1 to 3, characterized in that the burner or burners are connected in parallel to the exhaust pipe or pipes.

6. Process according to one of the preceding claims, characterized in that a regulating device is provided in the connecting pipe connecting the burner or burners to the supercharger.

7. Process according to claim 6, characterized in that the regulating device is formed by a valve, preferably a solenoid valve.

8. Process according to one of the claims 1 to 7, characterized in that for preventing the passage of exhaust gas to the supercharger a non-return valve is located in the connecting pipe.

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